Sql Identity (autonumber) is Incremented Even with a Transaction Rollback
SQL Server's identity columns are non-transactional, signifying the values increment regardless of transaction rollbacks. Rollbacks don't reset the identity value. Consequently, we have aftershocks in the form of gaps. This is an intentional design to side-step concurrent conflicts.
Here's an SQL Server showcasing this behaviour:
Even after a rollback, the identity value for the next insert rockets higher, bypassing the value from the rollback. If avoiding these gaps is a matter of life and death, opt for sequences with NO CACHE or manual key management.
Digging Deeper: Identity Mechanism
The Nuts and Bolts of Identity Columns
SQL Server's identity columns prioritize uniqueness and execution speed over sequential numbering. This performance-tuned mechanism is designed to keep your database running smoothly, avoiding potential trip wires of checking for the last inserted identity value.
Fallout of Non-Transactional IDs
The fallout of this smart mechanism is that identity gaps are inevitable in systems where transactions sometimes tumble and rollbacks occur. When a transaction rolls back, the incremented identity value doesn't get a do-over. Instead, it's discarded just like your commitment to the gym.
Going Sequential? Time for Custom IDs
If your system cries out for truly sequential IDs without gaps, it's time to roll up your sleeves and devise a custom ID generation strategy. Consider using sequences with NO CACHE, GUIDs or perhaps invent a time machine!
Coping with Gaps: It’s OK!
Truth is, most applications are unfazed by gaps in identity values. These gaps actually keep your database's integrity and consistency intact. Don't fight the gaps, they're not your enemy! #LoveTheGaps
Diving Further into Identity Increment Mechanics
Concurrent Transactions and the Identity Lifeguard
Auto-numbering being non-transactional isn't just a gimmick, it's a lifeguard preventing other transactions from drowning each other. This is crucial for ensuring your system basks in the sun of availability and performance during high-traffic periods.
Fixing the 'Gap' Problem
Trying to reclaim lost identity values during a rollback isn't just an uphill battle, it's hiking Everest in flip-flops. Design systems to expect these gaps, and you'll find yourself in smoother waters. These gaps have no impact on data logic or reference integrity, only on your perception of order.
Identity Increment and the Art of SQL Zen
If gaps in your auto-number sequence keep you up at night, it's a gentle nudge towards introspection on your database design. Weigh the consequences between the importance of sequentiality versus the performance advantages of non-transactional identities. You might stumble upon the path of database enlightenment.
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